The present invention relates to a cathode ray tube (CRT) and, more particularly, to a CRT that can reduce power consumption for deflecting electron beams by improving the structural characteristics of a funnel.
Generally, CRTs include a panel having an inner phosphor screen, a funnel having a cone portion, and a neck having an electron gun therein, which are sequentially connected to each other. A deflection yoke is mounted around the cone portion of the funnel to form horizontal and vertical magnetic fields there. In this structure, electron beams emitted from the electron gun are deflected through the horizontal and vertical magnetic fields from the deflection yoke, and land the phosphor screen.
Recently, CRTs have been employed for use in highly sophisticated electronic devices such as high definition television (HDTV) and OA equipment.
On the one hand, in these applications, the consumption of power of the CRT should be reduced to obtain good energy efficiency, and the leakage rom the magnetic field due to the power consumption should be reduced to protect the user from the harmful electronic waves. In order to cope with these requirements, it turns out that the consumption of power of the deflection yoke, which Is the major consumption source, should be reduced in a suitable manner.
On the other hand, in order to realize high brightness and resolution of display images on the screen, it Is required that the deflection power of the deflection yoke increase. Specifically speaking, higher anode voltage is required for enhancing brightness of the screen and, correspondingly, higher deflection voltage is required for deflecting the electron beams accelerated by she increased anode voltage. Furthermore, higher deflection frequency is required for enhancing resolution of the screen, and this accompanies the requirement of increased deflection power.
In addition, in order to realize relatively flat CRTs for more convenient use, wide-angle deflection should be performed with respect to the electron beams, and this also accompanies the requirement of increased deflection power.
In this situation, there are needs for developing techniques for allowing the CRTs to retain good deflection efficiency while constantly maintaining the deflection power or reducing it.
For this purpose, conventionally, a technique for increasing the deflection efficiency is introduced by positioning the deflection yoke to be closer to the electron beam paths. The positioning of the deflection yoke is usually achieved by reducing the diameter of the neck. However, in such a technique, as the diameter of the neck is reduced, the size of the electron gun to be mounted within the neck as well as the curvature of the funnel to be connected to the neck should be correspondingly varied, and this results in complicated processing steps. Furthermore, in such a structure, it turns out that the focusing characterist c of the electron gun poor.
Alernatively, in order to reduce the deflection power consumption, it is suggested that the diameter of the neck is constantly kept to be about 29.1xcfx86 and, instead, the neck-sided outer diameter of the funnel becomes smaller.
However, in such a structure, the electron beams to be applied onto the screen corner portions are liable to bombard the inner wall of the funnel adjacent to the neck (This phenomenon is usually called the xe2x80x9cbeam shadow reckxe2x80x9d or briefly the xe2x80x9cBSNxe2x80x9d). Consequently, the phosphors coated on the corresponding screen corner portions are not excited so that it becomes difficult to obtain good quality screen images.
In short, the techniques of decreasing the deflection power consumption simply by reducing the diameter of the neck or the neck-side outer diameter of the funnel necessarily involve the beam shadow, neck or other device failures because they cannot correctly deflect the practical moving routes of the electron beams.
It is an object of the present Invention to provide a CRT that is designed to reduce power consumption for deflecting electron beams without involving any beam shadow neck.
This and other objects may be achieved by a CRT with a central axis. The CRT includes a panel with an inner phosphor screen, and a funnel connected to the panel. The funnel has a cone portion with a neck sealing side, and a body portion extended from the cone portion to the panel. A deflection yoke is externally mounted around the funnel. A neck is connected to the neck sealing side of the cone portion. An electron gun is mounted within the neck.
The meeting point between the cone portion and the body portion indicated by a top of round (TOR). Furthermore, if two lines are drawn from the centers of the diagonal edges of the phosphor screen opposite to each other to a point of the tube axis line such that the angle between the tube axis line and each of the two lines reaches half the maximum deflection angle, a reference line (R/L) is indicated by the line crossing the point of the tube axis line normal thereto.
In this connection, the funnel is structured to satisfy the following condition:
0.52+0.001xc3x97(xcex1/2+xcfx86) less than b/a less than 0.74+0.001xc3x97(xcex1/2+xcfx86)
where a indicates the distance (mm) between he reference line R/L and the top of round TOR on the tube axis line, b indicates the distance (mm) between the reference line and the neck sealing side of the cone portion on the tube axis Z line, a indicates the deflection angle (degree), and xcfx86 indicates the diameter (mm) of the neck.